1. Field of the Invention
The present invention relates to a running control method and apparatus which runs an automatic guided vehicle as correcting its running position and direction by fixed points set on running courses.
2. Description of the Prior Art.
Automatic guided trackless vehicle which travels on the floor in a plant without attendant being developed and realized. There are two running systems as the running control system of the automatic guided vehicle, namely, an induction type and self-control type. The induction type travels automatically on the running course guided on optical reflecting tapes or wires energized with an electric current. The self-control type travels automatically in response to the running distance and direction of the running courses stored before traveling.
For the induction type, guides set as the running course must be checked and it was difficult to change the course.
While, aforesaid problems encountered by the induction type can be solved by the self-control type such that, for example, an operation unit for accumulating and operating pulses responsive to revolutions of left and right wheels is installed on the automatic guided vehicle, which is set at a starting position on the course, the number of pulses are counted successively simultaneously with the start of traveling to detect the position and direction of the vehicle, thereby guiding the vehicle to correspond to the running course stored in advance and to correct the position and direction at fixed points on the way to solve accumulated traveling errors.
As the prior art of self-control type, an optical system using an image pick-up device such as an ITV or the like and a magnet system invented by us (Japanese Patent Application No. 59-135514) are well known.
In the optical system, fixed points such as bar codes indicating coordinates positions of the plant are stuck to the floor surface, which are recognized by the image pick-up device to correct the running position and direction.
In the optical system, however, the fixed points stuck to the floor surface are subject to stains and influenced by ambient quantity of light, results in incorrect detection.
In addition, the ITV and its image processing devices are expensive and processing time is long, thus its application has been restricted.
Such problems of optical system may be solved by the magnet system mentioned hereinabove. In the aforesaid invention, a plurality of hall elements which detect the magnetic field intensity of magnets disposed at fixed points on the running course are aligned in a direction intersecting the moving direction of the vehicle, and since polarity differentials exist in outputs of the hall elements between left and right of the border right above the magnet, the relative position of the magnet and hall elements is calculated by detecting its variation point to correct the driving position and direction of the automatic guided vehicle.
In the invention aforementioned, however, since a plurality of hall elements are scanned serially by a CPU to detect the magnetic field intensity while traveling, detecting positions are differed for every hall element, and in practice, data are detected obliquely to the magnet, thus there was a fear that detecting errors of the magnetic field intensity may occur. When the magnetic field intensity is detected by one scanning while traveling, it is difficult to scan right above the magnet, and furthermore due to causes such as external noises, partial characteristic deteriorations and damages of hall elements or unstable outputs attributable to power fluctuations, malfunctions may be triggered.